Ketone–hemiacetal tautomerism in erythromycin A in non-aqueous solutions. An NMR spectroscopic study
- 1 January 1991
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 10,p. 1481-1487
- https://doi.org/10.1039/p29910001481
Abstract
NMR spectroscopic studies, including 13C SIMPLE NMR, in a number of solvents, show that erythromycin A exists as a mixture of the 9-ketone (the predominant species), one 6,9-cyclic hemiacetal 3(9-deoxo-6-deoxy-9-hydroxy-6,9-epoxyerythromycin A), and one 9,12-cyclic hemiacetal 2(9-deoxo-12-deoxy-9-hydroxy-9,12-epoxyerythromycin A). Similar studies on the 4″,11-diacetate of erythromycin A, previously thought to be the 6,9-cyclic hemiacetal, show that this exists exclusively as the 9,12-cyclic hemiacetal 4(9-deoxo-12-deoxy-9-hydroxy-9,12-epoxyerythromycin A 4″,11-diacetate) in CDCl3. The (9S) stereochemistry is proposed for 2, 3 and 4. The factors governing tautomerism in erythromycin A and its derivative are discussed.Keywords
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